Polycystic kidney disease (PKD) is a common hereditary disease and ranks fourth as a leading cause of end-stage renal failure. The primary goal of this study is to exploit volumetric imaging methods to identify and quantify morphologic measures that are associated with the PKD stage and the rate of PKD progression. 200 subjects, divided into three cohorts (GFR=30-50, 70- 90 ml/min) will be followed for a four-year period. Two participating clinical centers (PCC) will each contribute data on approximately 100 subjects. Each PCC will collect clinical data and specimens, perform renal functional tests, and obtain MR and US images for each subject at specific follow-up intervals. The data will be delivered or electronically transferred to the data coordinating and imaging analysis center (DCIAC) proposed in this application. Our specific aims are (1) to validate magnetic resonance (MR) volumetric imaging methods for accurate and reliable morphometric assessment of the renal parenchyma and renal/hepatic/pancreatic cysts in PKD patients; (2) to compare morphologic measures obtained from MR imaging data with renal functional measures in PKD patients to determine which morphologic measures are associated with the extent of renal functional impairment and with the rate of disease progression; and structural changes, while considering clinical-effectiveness, cost- effectiveness and patient acceptability. Statistical methods appropriate for growth curve estimation with a heterogeneous population will be developed and applied to characterize the PKD progression for each cohort and for the sample as a whole. The long-term goal of this project is to develop methods that would facilitate shortening the observation period necessary to determine efficacy of treatment interventions in PKD patients.